The notes you see are part of the PKGBUILD and/or installation script, you can get it without having to reinstall.

Firstly, download the package tarball (fakeroot pacman -b . -Syy && fakeroot pacman -b . --cachedir . -Sw package, or if you don't care about being root, pacman -Sw package) and extract it (tar xvzf package-*.tar.gz). Then you may view the PKGBUILD and .install files (if any), these will contain the information that you are looking for, and more.